1. Cut the peaches into thick chunks and discard the stones. Peel the ginger and grate it finely, then mash it to a wet paste with the flat side of a heavy knife. Put the peaches, sugar and ginger paste into a heavy-based pan and add the cinnamon stick.
2. Chop the chilli very finely and fold into the peaches along with the mustard seeds. Peel and finely chop the onions and grate the apples. Add to the pan, pour in the spiced vinegar and mint, and bring to a boil. Reduce the heat to a lazy and sloppy simmer, cooking for 1 hour until thick.
3. Remove the cinnamon stick and pour into bottling jars. Seal and store in a cool dark pantry.

Tip: The success of this dish relies on the peaches being ripe and sweet, to offset the saltiness of the prosciutto. Use golden queens or yellow-fleshed fruit.